運動過程除形成直接的能量負平衡外，其引發的激素調節作用亦可能具健康效益。Boström et al.（2012）發現了新的肌肉激素─irisin，其係透過運動刺激骨骼肌分泌，會促使脂肪產生棕 化（browning）現象而產熱耗能，或可調節骨骼肌本身的代謝作用。綜整目前探討運動介入對 irisin之效應的文獻可得，相較於運動訓練，單次運動較能使irisin濃度提升，此現象可能與代謝 恆定及適應有關；持續時間介於30分鐘至1小時，或強度較高之運動，多能顯著提升運動後立即 或短時間內的irisin濃度，而約在運動後1小時回復至基礎值。植基於目前各項研究結果，需持續 探討irisin的生理機制，此外，運動後肌肉損傷對irisin之影響，及irisin在運動能量代謝上的實際 作用，皆仍有待釐清。

Besides the negative energy balance resulting directly from exercise, it might trigger some hormone-regulated process which would bring beneficial effects to health. Irisin, newly identified by Boström et al. (2012), is an exercise-induced hormone secreted by contracting skeletal muscle, possibly mediating the positive effects of exercise on metabolism via inducing “browning” of white adipose tissue, and assumed to enhance skeletal muscle cell metabolism recently. Present studies of the effects of exercise on irisin show that elevated circulating irisin levels are often seen after an acute bout of exercise rather than chronic trainings; the circulating irisin concentration might reflect the energy state in body after exercise interventions, thus metabolic adaptations to training might affect the alteration of irisin levels. Exercises lasting for 30 minutes to 1 hour, or at high intensity would induce secretion of irisin. Elevated irisin levels are found immediately or in short periods after intervention and back to baseline in around 1 hour after exercise. The synthetic pathway and working mechanism of irisin require further examining, so do the reactions of irisin to muscle damages induced from exercises and the clinical role irisin plays in exercise metabolism in the future.

第一型解偶聯蛋白; 能量恆定; 代謝症候群

UCP1; energy homeostasis; metabolic syndrome